STILLWATER, Okla. -- Backup J.W. Walsh threw for 347 yards and four touchdowns in relief of injured starting quarterback Wes Lunt, leading Oklahoma State to a 65-24 blowout of Louisiana-Lafayette on Saturday.

Walsh also ran for 73 yards and a score after replacing Lunt, who hurt his left knee on the sixth play of the game and left the field on crutches.

The Cowboys (2-1) didn't miss a beat without him, scoring on their first eight possessions to build a 44-0 halftime lead and setting a school record with 742 yards of total offense.

Blake Jackson had 112 yards receiving and a touchdown, and Josh Stewart added 104 yards and two touchdowns through the air. Joseph Randle ran for 105 yards and two scores for Oklahoma State, which rebounded from a 59-38 loss at Arizona.

Blaine Gautier threw for one touchdown and ran for another for the Ragin' Cajuns (2-1). Gautier was benched for four series in the middle of the game, but backup Terrance Broadway -- who had filled in during a 37-24 win at Troy last week -- didn't fare much better.

For the Cowboys, it didn't seem to matter much who was taking the snaps.

Lunt stayed face down on the field for a few moments after getting hit by cornerback Melvin White as he scrambled backward and threw an incomplete pass on the Cowboys' first offensive series.

Walsh had his first pass attempt batted down two plays later, and Oklahoma State settled for a 51-yard field goal by Quinn Sharp. After that, Walsh led the Cowboys on five straight drives for touchdowns.

Walsh threw a 52-yard touchdown pass that fullback Kye Staley caught behind the line of scrimmage before zooming up the sideline behind blocks from a caravan of receivers, and Jackson jumped to catch a 20-yard TD pass one play after he'd made a 58-yard reception.

Stewart added scoring catches of 33 and 17 yards. Walsh, considered more of a running threat than Lunt, scored on a 4-yard keeper in the third quarter.

The Cowboys, who broke another school record with 39 first downs, surpassed their 725 yards of offense against Baylor in 2010.

Louisiana-Lafayette got its first touchdown when Gautier found Darryl Surgent wide open for a 73-yard pass after reserve cornerback Devin Hedgepeth crumpled to the ground with a left leg injury. Hedgepeth missed much of last season with a ruptured Achilles tendon and was playing as Oklahoma State started to rotate more bench players in.

Marcus Jackson added a 1-yard touchdown run and Brett Baer connected on a 41-yard field goal for the Ragin' Cajuns, who were trying to start 3-0 for the first time since 1988. Baer missed a 44-yarder in the first half, ending his streak of 18 straight made field goals.